Computational Fluid Dynamics (CFD)-Based Droplet Size Estimates in Emulsification Equipment

Abstract

While academic literature shows steady progress in combining multi-phase computational fluid dynamics (CFD) and population balance modelling (PBM) of emulsification processes, the computational burden of this approach is still too large for routine use in industry. The challenge, thus, is to link a sufficiently detailed flow analysis to the droplet behavior in a way that is both physically relevant and computationally manageable. In this research article we propose the use of single-phase CFD to map out the local maximum stable droplet diameter within a given device, based on well-known academic droplet break-up studies in quasi-steady 2D linear flows. The results of the latter are represented by analytical correlations for the critical capillary number, which are valid across a wide viscosity ratio range. Additionally, we suggest a parameter to assess how good the assumption of quasi-steady 2D flow is locally. The approach is demonstrated for a common lab-scale rotor-stator device (Ultra-Turrax, IKA-Werke GmbH, Staufen, Germany). It is found to provide useful insights with minimal additional user coding and little increase in computational effort compared to the single-phase CFD simulations of the flow field, as such. Some suggestions for further development are briefly discussed.

Twin-screw extrusion for the production of nanocellulose-PVA gels with a high solid content

“…For UT dispersion, the differential speed of rotation between the stator and the rotor induces a very high shear rate, typically about 4´10 4 s -1 at 22 000 rpm. In addition, in the intermeshing zone between the rotor and the stator, the fibers are submitted to an additional intense shear and elongational stresses (Janssen & Mayer, 2016).…”

Chemical and Process Engineering

“…The hydrodynamic field is represented by momentum and continuity conservation and details the local shear rates. The shear rate is then used by the population balance modelling to predict a drop size (Janssen and Mayer (2016) and Janssen and Hoogland (2014)). Power consumption comes from shear and pressure integration and will depend on gap size, viscosity and inlet mass flow rate (e.g.…”

Wave Characteristics of Coagulation Bath in Dry-Jet Wet-Spinning Process for Polyacrylonitrile Fiber Production Using Computational Fluid Dynamics

“…Computational fluid dynamics (CFD) has been shown as a powerful tool for analyzing single-phase hydrodynamics [2,3] as well as multiphase interactions [15][16][17][18]. The volume-of-fluid (VOF) CFD for multiphase flows is widely used for capturing interphase surface characteristics such as tracking the interface between gas and liquid phases in structured packing [19], and free-surface wave flow around a surface-piercing foil [20].…”